The present invention relates generally to the centrifugalization of fluids and, more specifically, to such a centrifugalization of blood or the like biological fluids in a closed system.
Heretofore, the following three processes have been generally used to centrifugalize, for example, blood into an erythrocytic, leukocytic, thrombocytic and plasmic fractions or to separate thrombocytes out of a mixture solution prepared, for a cleaning purpose, by mixing thawed lyophilized erythrocytes with a cleaning solution containing a cryophylactic agent:
(1) A bag containing the blood to be processed is set on a centrifugal separator, and the separator is operated for a sufficient time for separation. Then, centrifugalized fractions are taken out, in order from a fraction having the smallest specific gravity to one having the largest specific gravity, from a soft tubular section of the removed bag by manually compressing the same.
(2) The blood to be processed is fed into a frustoconical hollow container, to which conduits for feeding the blood and discharging the separated fractions are connected through rotary seals at its upper part. The blood fed into the container is centrifugalized into, for example a hematocytic fraction and plasmic fraction, and only the separated plasmic fraction, for example, is taken out through the discharge conduit, while the remaining hematocytic fraction is removed by stopping the operation of the centrifuge when the container is filled up with the hematocytic fraction.
(3) Blood to be processed is fed into a centrifugalizing container placed in a rotor of a centrifugal separator through one feed and discharge conduit which extends first downwardly from the central part of the rotor and then extends upwardly outside the rotor to be led to the outside of the centrifugal separator from a predetermined position above the rotor. The blood is centrifugalized by the rotation of the container and the separated fractions are taken out through the same conduit. This type of centrifugal separator may be used also for so-called blood cleaning by feeding a cleaning solution through the conduit into the centrifugalizing container.
These blood processing methods have been proposed for maximizing the quantity of an intended blood component fraction that can be gathered from one donor, since recently blood-component or fractional-blood transfusions have become increasingly generalized.
However, the foregoing method (1) is inefficient and time-consuming in that it is a batch processing method in nature, in which the centrifugal separator is operated intermittently and an additional operation is then carried out for transferring the separated fluids to other containers.
In the foregoing method (2), since the blood is continuously fed into the centrifugal separator and centrifugalized therein while discharging the unintended plasmic fraction, the intended erythrocytic fraction can be gathered in a larger quantity in one processing. However, this method is also hardly free from the afore-mentioned drawbacks of the method (1), because the quantity of the erythrocytic fraction that can be gathered by one processing are limited by the container capacity and because the centrifugal separator is also operated intermittently.
Also, since rotary seals are used in this method, the blood may be contaminated with bacteria intruding therefrom or abrasion particulates originating therefrom may be included in the blood, and such rotary seals requiring high sealing properties are costly. Further, in view of the construction of the centrifugal separator used in this method, it is not possible to process a plurality of fluids simultaneously.
In the foregoing method (3), although the centrifugal separator is operated continuously, the processing requires a longer time because the feeding of the blood and cleaning solution and the discharge of separated fractions are effected in order through a single common conduit. Also, since the conduit revolves outside the rotor along with its rotation, the centrifugal separator must be larger in size than those for the foregoing methods (1) and (2) to apply to the fluid in the container a centrifugal force almost equal to those applied in the methods (1) and (2). Thus, its construction becomes complicated and susceptible to problems. Further, since a long conduit is used in this method, a larger quantity of fluid remains therein after processing. Besides, since the conduit revolves about and outside the container along with its rotation, a large centrifugal force acts for a longer period on the fluid flowing through the conduit. Thus, the fluid may be separated undesirably in the conduit.
A typical prior art example of the foregoing method (3) and equipment therefor is disclosed in U.S. Pat. No. 4,133,173. In U.S. Pat. No. 4,133,173, however, since a conduit extends upwardly outside the rotor from the underside thereof, it is difficult to shorten the conduit. Also, in this prior art apparatus, the conduit revolves along with the rotor rotation and, thus, a substantial centrifugal force acts on the vertical section of the conduit because a long arm of action extends from the vertical axis of the rotor assembly. Thus, since such a large centrifugal force is applied to the fluid flowing through the vertical section of the conduit, the centrifugalization in the container installed in the rotor assembly may be adversely affected thereby.
In the aforecited U.S. Patent, the problem of twisting the conduit by the rotation of the rotor assembly is solved by setting the speed ratio of the rotor assembly versus a rotor drive assembly to 2:1.